What gas mixture for mig welding?

I am going to be doing a lot of butt welding of sheet metal very soon and I have a gas question. I have used 75/25% mix in the past and as I recall (been a couple of years) it worked ok. I tried a little practice weld the other day and I seemed to get more blow through more than I expected. I currently have one l bottle and it would have to be exchanged to try another mix. I thought I would ask the most experience group of people I know, V8Buick folks , before spending money on different gas just to find out I had the best gas for the job in the first place.

So, it I change to a lower percentage of argon will it help? How about straight CO2? Penetration is not an issue, I want cold and narrow beads.

Thanks, Kurt

 

Kurt,

Miller welds.com has some good reading http://www.millerwelds.com/resources/articles/sheet-metal-MIG-TIG-GMAW-GTAW

I would use .023 wire and use some form of chill block behind the weld. I have a piece of heavy copper. The weld wont stick to the copper.
You might want to try Esab easy grind wire
http://products.esabna.com/EN/home/..._id.id4367f2a958f8c3.05458256/category_id.504

 

Dave, thanks for the links. I think I just need to go out and practice on some more scrap before I start welding hand made patch panels for my rear window channel. I like the idea of a backing bar/chill bar. I wonder if I can get my wife to hold it in place while I do the welds? :grin:

What would be really cool is if I fabricated some brass or copper channels for run inert gas through behind the weld seam. they used to do that in a shop where I worked many years ago, it created a nice bead on the back side that was considered OK for seams that had to be cleaned in the food processing industry. Never did any of the that type of welding myself, they were in a different department making different machines.

 

Kurt,

Remember you wont be running a bead on thin sheet metal, just a series of tack welds making the seam.

 

Actual tack welds, not one inch skip welds?

 

It really depends on the amount of heat necessary to weld the material you are working with. You should start with tacks and should be able to go to alternating 1/4" stitches to minimize heat warp.

 

I did one inch welds and made a mess! Less heat is better.

 

i found tacks welds worked better one or two second bursts it will look like you tig welded it you can also reverse the polarity on your welded when welding thin material the gas is a huge help.when i welded my first floor pan in it was a mess the second pan i got some help setting the welder up with gas and what a difference.take your time

 

Lots of good advice given.
75/25 is the proper gas mixture.
Just tack tack tack. Make sure everything is clean shinny metal.

 

Thanks for all the help. A lot of tack welds it is. I'll let y'all know how it comes out.